Plasma display panels (hereinafter referred to as PDPs) are roughly categorized into two types: a DC type and an AC type. The mainstream of today's PDP is the AC type that is suitable for manufacturing large-size PDPs.
FIG. 16 is a partially sectioned perspective view, illustrating an example of AC type PDPs.
As shown in FIG. 16, a plurality of display electrodes 62 are disposed in stripes on a surface of a front glass substrate 61. A dielectric layer 63 is formed so as to cover the surface of the front glass substrate 61 and the display electrodes 62. Further, a dielectric protecting film 64 is formed over the dielectric layer 63.
On the other hand, a plurality of address electrodes 72 are disposed in stripes on a surface of a back glass substrate 71. The surface on which the address electrodes 72 are disposed faces the front glass substrate 61. The address electrodes 72 are disposed so as to become orthogonal with the display electrodes 62 when the front glass substrate 61 and the back glass substrate 71 are positioned facing each other. A dielectric layer 73 is formed so as to cover the surface of the back glass substrate 71 and the address electrodes 72. Further, on the dielectric layer 73, a plurality of barrier ribs 75 are disposed in parallel to the address electrodes 72, extending toward the front glass substrate 61.
A part surrounded by the dielectric layer 73 and two adjacent barrier ribs 75 is a groove, and phosphor layers 76 are disposed on inner walls of each groove. The phosphor layers 76 in the each grove are one of red phosphor layers 76R, green phosphor layers 76G, and blue phosphor layers 76B. The phosphor layers 76 are made of phosphor particles formed through a thick film formation process, such as screen printing, ink-jet, and photo resisting.
A discharge space is formed by the groove and the dielectric layer 64 when the front glass substrate 61 and the back glass substrate 71 having the above described constructions are positioned so as to face each other. A discharge gas is enclosed in the discharge space 77.
The AC type PDP having the above construction emits light based on basically the same principle as a fluorescent lamp. As discharging of electricity occurs in the discharge space 77, ultraviolet rays emitted from the discharge gas excite the phosphor layers 76 so as to convert the ultraviolet rays into visible light.
Note that the conversion efficiency of each phosphor material used for the phosphor layers 76R, 76G, or 76B is different. The color balance when an image is displayed on a panel is controlled by adjusting the luminance of each of the phosphor layers 76R, 76G, and 76B. Specifically, the luminance of the phosphor layers of other colors is lowered at a specific rate per color in accordance with the luminance of the color having the lowest luminance.
With increasing needs for high quality displays, PDPs having a finer cell structure have been demanded. When cells are made finer, volume of the discharge space 77 becomes smaller and radiation efficiency of the ultraviolet rays decreases. Therefore, it is necessary to further improve the luminous efficiency per cell in order to obtain PDPs having the fine cell structure.
A conventional NTSC has 640×480 cells, and a cell pitch for a 40-inch display of this kind is 0.43 mm×1.29 mm, an area per cell is 0.55 mm2, and the luminance is around 250 cd/m2 (“Function & Materials”, Vol. 16, No. 2, page 7, February, 1996, for example).
On the other hand, a high end hi-vision TV has 1920×1125 pixels, and a cell pitch for a 42-inch display of this kind is 0.15 mm×0.48 mm and an area per cell is 0.072 mm2. When a PDP for such a kind of hi-vision TV is manufactured using the conventional method, the radiation efficiency of the ultraviolet rays decreases down to 0.151-0.171 m/W, which is about 1/7 to ⅛ of NTSC. Accordingly, the luminous efficiency of the panel decreases as well.